Bernie Sanders never understood the epic quality of the Clinton scandals. In his first debate, he famously dismissed the email issue, it being beneath the dignity of a great revolutionary to deal in things so tawdry and straightforward.

Sanders failed to understand that Clinton scandals are sprawling, multilayered, complex things. They defy time and space. They grow and burrow.

The central problem with Hillary Clinton's emails was not the classified material. It wasn't the headline-making charge by the FBI director of her extreme carelessness in handling it.

That's a serious offense, to be sure, and could very well have been grounds for indictment. And it did damage her politically, exposing her sense of above-the-law entitlement and —in her dodges and prevarications, her parsing and evasions — demonstrating her arm's-length relationship with the truth.

But it was always something of a sideshow. The real question wasn't classification but: Why did she have a private server in the first place? She obviously lied about the purpose. It wasn't convenience. It was concealment. What exactly was she hiding?

Was this merely the prudent paranoia of someone who habitually walks the line of legality? After all, if she controls the server, she controls the evidence, and can destroy it — as she did 30,000 emails — at will.

But destroy what? Remember: She set up the system before even taking office. It's clear what she wanted to protect from scrutiny: Clinton Foundation business.

The foundation is a massive family enterprise disguised as a charity, an opaque and elaborate mechanism for sucking money from the rich and the tyrannous to be channeled to Clinton Inc. Its purpose is to maintain the Clintons' lifestyle (offices, travel, accommodations, etc.), secure profitable connections, produce favorable publicity and reliably employ a vast entourage of retainers, ready to serve today and at the coming Clinton Restoration.

Now we learn how the whole machine operated. Two weeks ago, emails began dribbling out showing foundation officials contacting State Department counterparts to ask favors for foundation "friends." Say, a meeting with the State Department's "substance person" on Lebanon for one particularly generous Lebanese-Nigerian billionaire.

Big deal, said the Clinton defenders. Low-level stuff. No involvement of the secretary herself. Until — drip, drip — the next batch revealed foundation requests for face time with the secretary herself. Such as one from the crown prince of Bahrain.

To be sure, Bahrain, home of the Fifth Fleet, is an important Persian Gulf ally. Its crown prince shouldn't have to go through a foundation — to which his government donated at least $50,000 — to get to the secretary. The fact that he did is telling.

Now, a further drip: The Associated Press found that over half the private interests who were granted phone or personal contact with Secretary Clinton — 85 of 154 — were donors to the foundation. Total contributions? As much as $156 million.

Current Clinton response? There was no quid pro quo.

What a long way we've come. This is the very last line of defense. Yes, it's obvious that access and influence were sold. But no one has demonstrated definitively that the donors received something tangible of value — a pipeline, a permit, a waiver, a favorable regulatory ruling — in exchange.

It's hard to believe the Clinton folks would be stupid enough to commit something so blatant to writing. Nonetheless, there might be an email allusion to some such conversation. With thousands more emails to come, who knows what lies beneath.

On the face of it, it's rather odd that a visible quid pro quo is the bright line for malfeasance. Anything short of that — the country is awash with political money that buys access — is deemed acceptable. As Donald Trump says of his own donation-giving days, "when I need something from them . . . I call them, they are there for me." This is considered routine and unremarkable.

It's not until a Rolex shows up on your wrist that you get indicted. Or you are found to have dangled a Senate appointment for cash. Then, like Rod Blagojevich, you go to jail. (He got 14 years.)

Yet we are hardly bothered by the routine practice of presidents rewarding big donors with cushy ambassadorships, appointments to portentous boards or invitations to state dinners.

The bright line seems to be outright bribery. Anything short of that is considered — not just for the Clintons, for everyone — acceptable corruption.

It's a sorry standard. And right now it is Hillary Clinton's saving grace.

Charles Krauhammer is a Pulitzer Prize-winning syndicated columnist, published weekly in more than 400 newspapers worldwide. From 2001 to 2006, he served on the president's Council on Bioethics. He is author of The New York Times best-seller "Things That Matter: Three Decades of Passions, Pastimes and Politics." For more of Charles Krauthammer's reports, Go Here Now.

We are hardly bothered by presidents rewarding big donors. The bright line seems to be outright bribery. Anything short of that is considered, not just for the Clintons, for everyone, acceptable corruption. It's a sorry standard; now it's Hillary Clinton's saving grace.